Biochar is a highly porous carbonized material that can be found on the soil after a forest has burned. The porous nature of biochar and other charcoal products has been found to provide a habitat for beneficial microbes that absorb toxins in the soil and convert organic detritus into useful materials for the growth of nascent plants.
Synthetic charcoal products and biochar can be made on an industrial scale by burning wood chips and other cellulosic materials in an oxygen deficient atmosphere. Biochar in particular has a remedial benefit on the soil due mainly to the highly porous nature of the charcoal it contains. These pores are able to absorb toxic metals and accommodate beneficial microbes that feed on the remaining organics, leaving the soil fit for plant growth.
Synthetic biochar is made and traded worldwide. It is used mainly for soil remediation and improved plant growth. Early manufacturing processes were essentially based upon those for making pure charcoal. The feedstock can be any cellulose containing material that will breakdown under anoxic conditions to produce charcoal. Wood chips are preferred. Although the cellulose in the wood decomposes mainly to carbon and water, at high temperatures, a side reaction converts some charcoal into biogases and bioliquids. As biochar is not a pure charcoal, it is sold at a lower price. The reaction by-products reduce the value further, as they are only marketable as cheap fuel.
The particles of synthetic biochar may be distributed on the soil with equipment used for other agricultural products, such as plant seed and pelletized fertilizer. However, since the charcoal in the biochar is somewhat friable, distribution using conventional agriculture equipment creates hazardous dust, and loss of useful product. Furthermore, the low bulk density and lack of particle sizing control of the biochar causes separation of any blend of biochar and plant seed and/or commercial fertilizer during handling and distribution. To overcome this problem, methods have been developed to protect the biochar particles with a layer of an inert ceramic material. This approach has been found to minimize product breakdown and increase bulk density. As the ceramic coating needs to be sintered at high temperature, undesirable by-products are formed at the expense of some of the charcoal. Also, the inert coating simply disintegrates into small particles that remain in the soil.
It should be noted that biochar may also be used in other industries. Biodiesel for sale as transportation fuel in Canada and the United States must meet strict quality guidelines (CAN/CGSB-3.524-2011 in Canada and ASTM 6751 in the U.S.). Biodiesel must have low water and glycerol content. Often biodiesel manufacturers must use post-manufacturing desiccants and absorptive resins to remove unwanted contaminants before the quality of the biodiesel is sufficient for sale. This is sometimes referred to as “polishing.” A biochar-based polishing agent would be advantageous because it is environmentally benign unlike some polymeric polishing agents. Thus, disposal of the bio-based based agent after polishing may be seen as having less of a negative impact. Because biochar is dusty and comprised of small particles that would contaminate the biodiesel, using un-pelleted biochar is not an option to absorb unwanted liquid contaminants such as water from transportation fuel. However, if biochar is densified into pellets that are robust and non-dusty, the product can be used as a polishing agent without introducing further contamination.
A biochar product that can be used as noted above would therefore be advantageous. Not only that, but a process for producing such a product, with mechanical properties that allow its use in the biodiesel industry, would also be advantageous and desirable.